what type of signal the megasquirt send to the igniters? a ground or a 5v signal?

 

I want to run 3 msd 6a from that signal it is posible?

 

The rotary configured outputs and coil/igniters go high to charge, low to fire. In some configurations, possibly even the code in rotary mode ( but I'm not sure and can't look at the moment), the ign outputs are configurable as to output. I'm not personally familiar with the MSD boxes but am certain other MS users have utilized them successfully.